A Question of Mind Over Matter

In 2001, Jesse Sullivan was the first person to test this biohybrid arm, created by the Rehabilitation Institute of Chicago. It allows an amputee to move the prosthetic by thought alone. Five more amputees, including the first woman, are now testing the arm.

MIT assistant professor Hugh Herr is an advanced prosthetics researcher and a bilateral leg amputee, two conditions that have allowed him the rare experience of testing his gadgets on himself.

"You know how it feels when you're at the airport and you hit the moving walkway? It's kind of like that," he said of a new foot-ankle system he's developing with colleagues at MIT, Brown University and the VA Medical Center in Providence, Rhode Island.

The so-called biohybrid system sports a power pack and computer all contained within the prosthesis and uses sensors to allow more realistic movements than static, strap-on devices. The first systems have noninvasive sensors attached to the prostheses. In about two years scientists will implant sensors into study volunteers' nervous systems, Herr said.

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DIY Prosthetics
Amputees who can't find the right prosthetics on the market build their own — sometimes out of Legos. By Quinn Norton.

Grow Your Own Limbs
Scientists are learning how amputees might eschew the prosthetic and grow back missing limbs. By Kristen Philipkoski.

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What if bionics get so good that we want them even if we don't need them? By Chris Oakes.

"I've been an engineer-designer for a long time, but this is the first system (from which) I can benefit personally," he said. "It's kind of fun. I don't know why I waited this long."

Herr's enthusiasm is perhaps understandable, given his disability. But, in light of the immense strides scientists have achieved in prosthetics in the past decade, it is also well grounded. Improvements in materials for comfort and performance are part of the story. Of equal significance, scientists are probing the limits of mind-body interaction, developing tools that use artificial intelligence, muscle and neuron sensors — and even plugging directly into the brain — to achieve unprecedented results. Some patients need only to think to make a machine do their bidding.

The aggressiveness of the research has taken some people aback. "I would look under the hood and make sure the technology is as developed and is as good as they say it is," said Andrew Imparato, president and CEO of the American Association of People with Disabilities.

Even so, he added, further research could yield enormous benefits. "I think there's a lot about the human brain we don't fully comprehend. So if scientists are tapping into the brain to let people do things we haven't been able to do before, that's exciting," he said.

A breakthough could transform the lives of millions of people. The Amputee Coalition of America estimates between 1.8 and 1.9 million people in the United States live with some type of limb loss.

So just how close are we to a seamless blending of man and machine? In this four-part series, we take a look at some of the most promising — and astonishing — recent developments, from cutting-edge research labs to do-it-yourself garage mechanics that are changing our ideas of the body and its boundaries.

The Bionic Arm

In 2001, Jesse Sullivan, a high-power lineman, was nearly electrocuted and so badly injured that doctors had to amputate both of his arms. In 2002, he became the poster boy for the bionic arm when he appeared on national television wielding a computerized, biohybrid arm created by scientists at the Rehabilitation Institute of Chicago. On Thursday, Sullivan and the first woman to test the bionic arm, Claudia Mitchell, demonstrated their new abilities with the arm. Sullivan told reporters he can now trim hedges and mow the lawn. Mitchell, who lost her arm in a motorcycle accident, said the arm allows her to carry a laundry basket and fold clothes.

The researchers implant sensors within the pectoral muscles, attaching them to nerves that controlled elbows, wrists and hands before the amputations. The arm takes advantage of the fact that the brain can imagine moving an arm that isn't there — a sometimes-unwelcome phenomenon for amputees known as "phantom arm" that can even involve pain in the missing limb.

Since the brain is still sending signals to the arm, the device can hijack messages telling muscles to move, or to feel touch or temperature. The researchers attach sensors from the device to the nerves, which attach and become intertwined with the nerves over time as the patient thinks about moving the arm.

When the prosthesis is strapped on, electrodes line up with the sensors to control the computer and motors in the bionic arm to operate the hand — and all the user has to do is think.

The rewiring can causes minor side effects: "If you touch Jesse on his chest in certain places, he can feel it like it's his hand," said Todd Kuiken, director of the institute's Neural Engineering Center for Artificial Limbs, which developed the technology.

Five more amputees, including Mitchell, are now testing biohybrid arms. In the lab they use fancier arms with six motors, while the take-home version has three. Four of the volunteers are unilateral amputees, while one, like Jesse, has lost both limbs. All have received nerve implants, and the system is working for all but one patient, Kuiken said. The National Institutes of Health has provided $2 million of the $3 million Kuiken's lab has spent developing the arm.

A bionic leg is next on Kuiken's to-do list — as prosthetic companies develop motorized legs, Kuiken hopes to adapt his technology to control them.

The Mind Reader

Cyberkinetics' brain-computer interface, BrainGate, is a breakthrough device for people with spinal cord injuries. Plugged directly into the brain, the device allows paralyzed people to control a computer, flip switches and move a robotic hand — by simply thinking.

The researchers recorded cortical activity from an ALS (Lou Gehrig's disease) patient. Another study volunteer who can't speak after a brainstem stroke used the BrainGate to type.

The brain implant sends signals to an external amplifier, which sends the messages through software that generates cursor movements or other electronic activity. The test system is wired, but the company's scientists say the final product will be wireless.

Surgenor hopes BrainGate will be FDA-approved in about four years.

The Second Sight

Blind patients were granted sight earlier this year in exchange for participating in a clinical trial testing a wireless retinal implant.

"If you talk to those people, even one single dot makes a difference," said Hans-Gurgen Tiedtke, CEO of IIP-Technologies.

The system includes glasses featuring a wireless transmitter and a mini-camera to pick up images. The glasses connect by cable to a processor pack worn at the waist that analyzes the information like a retina would, then send the image information to a chip implanted in the retina. The chip electrically stimulates the retina so ganglion cells can pick up the images. From there, the process continues like it would in a healthy eye: the information goes to the optic nerve, then to the brain and visual cortex where the information is reassembled as a picture.

It won't restore 20/20 vision, but researchers hope patients can eventually identify doors, chairs and windows, Tiedtke said, and perhaps even pick out faces.

The study volunteers received a beta version of the system. The companies plan to launch a second clinical trial with an updated version of the technology by the end of September. Tiedtke hopes the device will be commercially available in Europe in 2008, and in the United States soon afterwards.

The Universal Prosthetic for Kids

Adults can often use one prosthetic for years. But children are constantly growing, meaning their prosthetics must be replaced as often as every six months. So Tom Chau, a scientist at Bloorview Kids Rehab in Toronto, is developing a control system that will remain a constant link between the child and the prosthetic. It will adapt to growing boys and girls, and attach to various sizes of prosthetic hands.

"Part of the solution to this problem of the child being so dynamic is you need to be able to recycle some of these components," Chau said.

Chau's system uses silicone-encased sensors with microphones that capture muscle noises. A microcontroller in the prosthetic filters out background noise and determines how the hand should move.

The prosthesis could help children participate even in high-energy activities because sweat won't interfere with the sensors, Chau said. It could even be waterproofed for swimmers.

He's first testing prototypes on adults because they generate stronger muscle signals, which makes it easier to test. Plus, they can sit still longer.

The High-Tech Knee

South Africa's Oscar Pistorius set a world record this month in the 200-meter dash at the 2006 Paralympic Athletics World Championship, using specialized "blades" to clock a time of 21.66 seconds — fast enough to best the men's Olympic gold medal time of 22 seconds flat in 1920.

If it's exciting to watch athletes compete in running events using slick, custom prostheses, in reality such devices are more useful in a competitive sprint than getting around the house.

Bethesda, Maryland-based Hanger Orthopedic Group has helped many amputees excel athletically with high-tech prostheses. But they're also helping people with more mundane but equally important activities like walking to the bus stop or feeding themselves.

And just because the tasks are more pedestrian doesn't mean the scientists are skimping on technology. The Power Knee, for example, uses artificial intelligence to help amputees walk, get out of chairs and clear steps more naturally. The knee has motor-driven power, and an ankle sensor. On the patient's functional leg, the user wears a computerized shoe insole, which communicates with the prosthesis.

"For the first time, your left and your right foot are working together in unison. It gives you a much more stable, much more natural gait," said Dale Berry, Hanger's vice president of clinical operations. It also reduces stress on the body.

The knee system became available earlier this year for $100,000. Some customers might experience sticker shock since prosthetics that use hydraulics cost $20,000. But Berry thinks customers will be willing to pay for the improved gait.

Hanger is also working with Ossur to create a foot-ankle device that automatically adjusts to heights whether the user is walking barefoot or wearing a 1.5-inch heel. It should use less energy and look more natural than other devices, Berry said. "No other prosthetic foot can do this."

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